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Thread: Expansion tank sizing

  1. #1
    DIY Senior Member rockycmt's Avatar
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    Default Expansion tank sizing

    Can you help recommend a brand/size expansion tank for my HW system.

    I currently have one but it is a large, old, steal, bladderless tank recessed in the ceiling. I need to remove it anyways cause I have to sheetrock around the boiler so I am deciding to replace it.

    I have a 4 bedroom 2000 sf cape
    Full basement
    2 bath

    http://www.watts.com/pdf/1915356.pdf
    Last edited by Terry; 10-27-2008 at 11:30 AM.

  2. #2
    Master Plumber nhmaster's Avatar
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    Nope. Need to know volume and head pressure.

  3. #3
    Retired Defense Industry Engineer jadnashua's Avatar
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    Watts has a calculator on their website you can use. You'll need to know some stats for your heating system to get it right.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  4. #4
    DIY Senior Member rockycmt's Avatar
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    Do I only need to take into consideration the volume of my boiler or all the piping as well? If so, how do I estimate the 1' copper lengths throughout the house?

  5. #5
    Retired Defense Industry Engineer jadnashua's Avatar
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    You need the total volume of water, since all of it can expand and contract. Volume of a cylinder is pi*r^2*length. If you get a guess at the total length of pipe, you'll be close. But, I assume those pipes run to radiators? Unless they are finned baseboard, they'll add some. If you get a good approximation, the tanks have a fair range, you should be able to properly select one. there are 231 cubic inches in a gallon.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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